1. Field of the Invention
The present invention relates to a method of an apparatus for fabricating a semiconductor substrate having a very shallow impurity diffusion layer which is suitable for a high-frequency transistor device and a large scale integrated circuit device.
2. Description of the Background Art
A semiconductor substrate is generally fabricated by doping predetermined impurities into a semiconductor wafer to form an impurity diffusion layer on the surface of the semiconductor wafer.
Examples of a method of forming an impurity diffusion layer are generally a process of annealing impurities after pre-deposition, ion implantation, and epitaxial growth.
Meanwhile, it is preferable that a semiconductor device provided with a shallower impurity diffusion layer is used in terms of increasing the response speed in a high-frequency transistor device and increasing the integration density in a large scale integrated circuit device. Ion implantation is generally employed so as to fabricate such a semiconductor device.
However, it is difficult to form a shallow P-type diffusion layer using ion implantation, although a shallow N-type diffusion layer is formed to some extent using arsenic ion implantation.
Furthermore, examples of a method of forming a very shallow diffusion layer having a thickness of approximately 0.1 .mu.m are low energy boron ion implantation, BF.sup.2 implantation, and double implantation of boron and silicon ions. The methods have a lot of problems in terms of apparatus and process technology.